Techniques for imaging a scanned object

ABSTRACT

A technique for enhancing an image includes manipulating a base image to highlight pixels showing a particular material based on the energy absorption information of each pixel. In another technique, pixels in a base image are each converted to an output value to produce a converted image. Another technique allows imaging an obstructed object within a base image which is made of pixels, each representing a captured signal from a source emitting a source signal I 0 . An obstruction region contains pixels representing a combined signal I 3  having traversed the obstructed object and an obstructive layer. Knowing a layer signal I 2  representing a signal having traversed the obstructive layer outside of the obstruction region, the layer signal I 2  may be removed from the combined signal I 3 , in order to reveal the original signal I 1  representing an image of the obstructed object.

FIELD

The present relates to the field of image processing. More particularly,the present invention relates to a system and method for detecting amaterial in an object, to a system and method for enhancing a display ofa base image of an object, and to a system and method for imaging anobstructed object in an image.

BACKGROUND OF THE INVENTION

Conventional scanning systems display images of a scanned object for anobserver to view elements of the scanned object.

Given that the human eye is only able to distinguish a certain level ofcontrast in an image, especially in greyscale, there is a need for asystem which displays images in an improved manner so as to help anobserver better distinguish elements in an image of a scanned object.

Hence, in light of the aforementioned, there is a need for an improvedsystem which, by virtue of its design and components, would be able toovercome some of the above-discussed prior art concerns.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an improved imagedisplay system.

In accordance with an aspect, there is provided a method for detecting amaterial in an object. The method comprises: receiving, via an inputport, a base image of the object comprising one or more material to bedetected, the base image being composed of pixels, each pixel comprisingenergy absorption information; providing in a memory, one or morereference value, each representing an energy absorption of a referencematerial; transforming the base image, by means of a material detectionmodule embedded in a processor, by highlighting each of said pixels ofwhich the energy absorption information correlates with one of saidreference material stored in the memory, based on a comparison of theenergy absorption information of each pixel with said one or morereference value stored in the memory, in order to produce adetection-enhanced image; and displaying, on a display screen, thedetection-enhanced image having highlighted pixels corresponding to saidone or more material to be detected.

According to embodiments, the base image is generated by capturing asource emission, for example an X-Ray emission, having traversed theobject and by converting said source emission to a pixel value.According to embodiments, each reference value is set for a given signallevel of the source emission and the comparison between the energyabsorption information of the pixel and the one or more reference valuein the transforming step, takes into account the signal level. In someembodiments, the source emission to which the object is subjected to,corresponds to this signal level.

According to embodiments, the energy absorption information comprises anatomic number.

According to embodiments, the energy absorption information of eachpixel comprises a low energy absorption component and a high energyabsorption component. The low energy absorption and the high energyabsorption components may be converted into a corresponding grey scalevalue for the pixel, representing the particular combination of low andhigh energy absorption. According to some embodiments, the referencevalue comprises a low energy reference value and a high energy referencevalue for each of said reference material, in which case the comparisonbetween the energy absorption information of the pixel and the one ormore reference value in the transforming step, comprises: comparing thelow energy absorption information with the low energy reference value;and comparing the high energy absorption information with the highenergy reference value. The low energy reference value and the lowenergy absorption information may correspond to an energy signal withina lower range spanning between about 10 kV to about 70 kV. The highenergy reference value and the high energy absorption information maycorrespond to an energy signal within a higher range spanning betweenabout 60 kV to about 250 kV. In some embodiments, the higher range mayreach much higher values for example, up to about 6 MeV.

According to embodiments, the reference material is a particular metal.

According to embodiments, the reference values represent energyabsorptions of a plurality of reference materials.

According to embodiments, the highlighting step comprises coloring thepixel to be highlighted in a contrasting color, in relation to otherpixels in the detection-enhanced image.

According to embodiments, the method further comprises receiving, via auser input device, a requested material to be detected. In suchembodiments, the reference material of the transforming step correspondsto the requested material, so as to highlight the pixels correspondingto the requested material in the detection-enhanced image of the object.

In accordance with another aspect, there is provided processor-readablestorage medium for detecting a material in an object, theprocessor-readable product comprising data and instructions forexecution by a processor, to execute steps of the above-mentionedmethod.

According to embodiments, the processor-readable storage medium is anon-transitory product.

In accordance with another aspect, there is provided a system fordetecting a material in an object. The system comprises: an input portfor receiving a base image of the object comprising one or more materialto be detected, the base image being composed of pixels, each pixelcomprising energy absorption information; a memory for providing one ormore reference value, each representing an energy absorption of areference material; a material detection module embedded in a processor,the processor being in communication with the input port and the memory,for transforming the base image by highlighting each of said pixels ofwhich the energy absorption information correlates with one of saidreference material stored in the memory, based on a comparison of theenergy absorption information of each pixel with said one or morereference value stored in the memory, in order to produce adetection-enhanced image; and a display screen being in communicationwith the processor, for displaying the detection-enhanced image havinghighlighted pixels corresponding to said one or more material to bedetected.

In accordance with yet another aspect, there is provided a method ofenhancing a display of a base image of an object. The method comprisesreceiving, via an input port, a base image comprising pixels, each pixelhaving an intensity value; providing in a memory, one or more referenceintensity, each being associated to an output value; transforming thebase image, by means of a conversion module embedded in a processor, toconvert pixels of the base image into to the associated output values,by correlating the intensity value of each pixel with said one or morereference intensity stored in the memory, to produce a converted image;and displaying the converted image, on a display screen.

According to an embodiment, the intensity value of the receiving steprepresents an intensity level within a monochromatic scale. Thereference intensity(s) stored in the memory comprises ranges of themonochromatic scale, wherein the output value stored comprises an outputcolor for each range. The transforming comprises converting each pixelfrom said monochromatic scale to a corresponding one of said outputcolor, such that the converted image is a color-mapped image. In suchembodiments, each range of the monochromatic scale may be associated toa spectrum of color, and the output value may be selected by correlatinga position of the intensity value of the pixel within said range, with acorresponding position within said spectrum of color. In addition, eachrange of the monochromatic scale stored in the memory may be associatedto a distinct color. Further, adjacent ranges of the monochromatic scalestored in the memory may correspond to contrasting colors.

According to embodiments, the transforming further comprises defining aregion of interest in the base image, and wherein the pixels of theconverting step are within the region of interest. The region ofinterest includes to the entire base image or a portion or portions ofthe base image. In such embodiments, the transforming further comprisesprior to the converting step: defining a scale of intensity valuesincluding the intensity values of the pixels in the region of interest;and stretching said scale by applying a multiplying factor to theintensity values of said pixels in the region of interest, in order toenhance variations of in the intensity values of the pixels within theregion of interest. The region of interest may be defined based on auser selection received. Alternatively, the region of interest may bedefined by identifying, by means of the processor, a region in the baseimage containing pixels which exceeds a threshold intensity. Thethreshold intensity may be set to define the region of interest toinclude portions of the image having a predetermined number of pixelshaving a low intensity value.

According to embodiments, the transforming and displaying steps arerepeated for a plurality of iterations, in order to modify the displayedimage within a period of time. For example, the method may furthercomprise: defining, at a first iteration, a first section comprising thepixels of the converting step of said first iteration; and at a seconditeration, defining a second section comprising the pixels of theconverting step of said second iteration. The second section maycorrespond to a section adjacent to the first section within the baseimage. In another example, the method further comprises: at a firstiteration, prior to the converting step: defining a first threshold ofintensity, filtering out pixels having an intensity value which exceedssaid first threshold to keep only unfiltered pixels of the firstiteration, and multiplying the intensity values of the unfiltered pixelsby a factor; and at a second iteration, prior to the converting step:defining a second threshold of intensity different from said firstthreshold, filtering out pixels having an intensity value which exceedssaid second threshold to keep only unfiltered pixels of the seconditeration, and multiplying the intensity values of the unfiltered pixelsby said factor.

According to embodiments, the output value associated to the one or morereference intensity is further changed between successive iterations.The output value may be selected from a color scheme changing over atime period. The color scheme may further transition periodically insine waves.

According to embodiments, the intensity value of each pixel represents asignal intensity of the object having been subjected to a sourceemission. The signal intensity may correspond to an energy absorption.The source emission may be an X-Ray source.

In accordance with another aspect, there is provided aprocessor-readable storage medium for enhancing a display of a baseimage of an object, the processor-readable product comprising data andinstructions for execution by a processor, to execute steps of theabove-mentioned method. The processor-readable storage medium may be anon-transitory product.

In accordance with another aspect, there is provided a system forenhancing a display of a base image of an object. The system comprisesan input port for receiving a base image comprising pixels, each pixelhaving an intensity value; a memory for providing one or more referenceintensity, each being associated to an output value; a conversion moduleembedded in a processor, the processor being in communication with theinput port and the memory for transforming the base image in order toconvert pixels of the base image into to the associated output values,by correlating the intensity value of each pixel with said one or morereference intensity stored in the memory, and to produce a convertedimage; and a display screen displaying the converted image.

In accordance with still another aspect, there is provided method ofimaging an obstructed object in an image. The method comprises:receiving, via an input port, a base image comprising pixels, eachrepresenting a captured signal from a source emitting a source signalI₀; locating, by means of a locating module embedded in a processor, aregion of interest in the base image wherein the pixels represent acombined signal I₃ having traversed the obstructed object and saidobstructive layer; providing, in a memory, a layer signal I₂representing a signal having traversed the obstructive layer outside ofsaid region of interest; isolating, by means of a calculator embedded inthe processor, an original signal I₁ in said region of interest, byremoving for each pixel in said region of interest, the layer signal I₂from the combined signal I₃, on the basis of said source signal I₀, theresulting original signal I₁ representing an image of the obstructedobject; and displaying on a display screen, a resulting image from saidoriginal signals I₁, wherein the region of interest reveals theobstructed object. The source signal may be sourced from an X-Rayemission.

According to embodiments, the isolating step is based on theBeer-Lambert Law. More particularly, the original signal is obtainedaccording to the following equation:

$I_{1} = {{( {I_{3} \cdot I_{0}} )/I_{2}} = {\frac{I_{0}^{2}( {^{{- \mu_{1}}t_{1}} \cdot ^{{- \mu_{2}}t_{2}}} )}{I_{0}^{{- \mu_{2}}t_{2}}} = {I_{0}^{{- \mu_{1}}t_{1}}}}}$

wherein I₁=I₀e^(−μ) ¹ ^(t) ¹ ,where μ₁ represents an attenuation coefficient of the obstructed objectand t₁ represents a thickness of the obstructed object; andwherein I₂=I₀e^(−μ) ² ^(t) ² ,where μ₂ represents an attenuation coefficient of the obstructive layerand t₂ represents a thickness of the obstructive layer.

According to embodiments, the source signal I₀ represents a low energycomponent of a source signal, wherein the layer signal I₂ represents alow energy component of the signal having traversed the obstructivelayer outside of said region of interest, wherein the combined signal I₃represents a low energy component of the signal having traversed theobstructed object and said obstructive layer, and wherein the resultingoriginal signals represents a low energy component of a signalrepresenting the obstructed object when unobstructed.

According to embodiments, the source signal I₀ represents a high energycomponent of a source signal, wherein the layer signal I₂ represents ahigh energy component of the signal having traversed the obstructivelayer outside of said region of interest, wherein the combined signal I₃represents a high energy component of the signal having traversed theobstructed object and said obstructive layer, and wherein the resultingoriginal signals represents a high energy component of a signalrepresenting the obstructed object when unobstructed.

In accordance with another aspect, there is provided aprocessor-readable storage medium for imaging an obstructed object in animage, the processor-readable product comprising data and instructionsfor execution by a processor, to execute steps of the above-mentionedmethod.

According to an embodiment, the processor-readable storage medium is anon-transitory product.

In accordance with another aspect, there is provided a system forimaging an obstructed object in an image. The system comprises: an inputport for receiving a base image comprising pixels, each representing acaptured signal from a source emitting a source signal I₀; a locatingmodule embedded in a processor, the processor being in communicationwith the input port for locating a region of interest in the base imagewherein the pixels represent a combined signal I₃ having traversed theobstructed object and said obstructive layer; a memory for providing alayer signal I₂ representing a signal having traversed the obstructivelayer outside of said region of interest; a calculator embedded in theprocessor, for isolating an original signal I₁ in said region ofinterest, by removing for each pixel in said region of interest, thelayer signal I₂ from the combined signal I₃, on the basis of said sourcesignal I₀, the resulting original signal I₁ representing an image of theobstructed object; and a display screen for displaying a resulting imagefrom said original signals I₁, wherein the region of interest revealsthe obstructed object.

The objects, advantages and features of the present invention willbecome more apparent upon reading of the following non-restrictivedescription of preferred embodiments thereof, given for the purpose ofexemplification only, with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of the image display system,according to an embodiment of the present invention.

FIG. 2 shows the contents of a suitcase to be scanned, in the context ofa precious metal detection module within the system shown in FIG. 1.

FIG. 3 is a scan image of the suitcase shown in FIG. 2.

FIG. 4 shows the scan image of FIG. 3, when the precious metal detectionmodule is activated.

FIG. 5 is an image of an object having been scanned by the scanningsystem, according to an embodiment of the present invention.

FIG. 6 is a histogram of the image shown in FIG. 5.

FIG. 7 is the histogram of FIG. 6, after cancellation of some of thesignal by the dynamic range variation module of the system shown in FIG.1.

FIG. 8 is a histogram of FIG. 7, after stretching the remaining signalby the dynamic range variation module of the system shown in FIG. 1.

FIG. 9 is a version of the image shown in FIG. 5, after the stretchingof the signal by the dynamic range variation module.

FIG. 10 is a diagram showing the color conversion of the dynamic rangevariation module.

FIG. 11 is an image generated by the dynamic range variation module,from the basis of the image shown in FIG. 5.

FIGS. 12A and 12B show steps during a first sweeping display mode of thedynamic range variation module.

FIG. FIG. 13A to 13D shows steps during a second sweeping display modeof the dynamic range variation module.

FIG. 14 is a diagram showing a conversion of the dynamic range variationmodule in a grey scale, according to an alternate embodiment.

FIG. 15 is a diagram showing a conversion of the dynamic range variationmodule, according to another alternate embodiment.

FIG. 16A to 16D show different screen captures illustrating theoperation of the sinusoidal color map module of FIG. 1.

FIG. 17 is a diagram showing a Beer-Lambert law theorem applied by thelayer removal module of the system shown in FIG. 1.

FIG. 18 shows images displayed further to a formatting by the layerremoval module.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

In the following description, the same numerical references refer tosimilar elements. The embodiments mentioned and/or geometricalconfigurations and dimensions shown in the figures or described in thepresent description are embodiments of the present invention only, givenfor exemplification purposes only.

Broadly described, the image display system according to a particularembodiment of the present invention, as exemplified in the accompanyingdrawings, provides a base image from which information is extracted inorder to display it in a desired format, so as to enhance the visualexperience of an observer.

In accordance with an embodiment, as better illustrated in FIG. 1, thereis provided an image display system 10 comprising:

-   -   a storage 12 for storing a base image of a scanned object, the        base image being composed of pixels each having a display value,        which may correspond to a greyscale or color value;    -   an input/output port 16, at a processor 14, for receiving the        base image and a display format selection;    -   a formatting module 18, integrated in the processor 14, for        formatting the image according to the display format selection;    -   an input/output port 20 at the processor 14 for transmitting a        formatted image to be displayed; and    -   a display 22, integrated in a user interface, for displaying a        formatted image, in order to provide a better distinction in        elements constituting the scanned object.

Base Image

In accordance with an embodiment of the present invention, the baseimage is generated by scanning an object using X-Ray radiation.

More particularly, a source emits electromagnetic (or EM) radiation,such as X-rays, toward an object. The emission of the EM radiation maybe performed continuously, at discrete intervals, or only as the objectdisplaced in relation to the source. Detectors located opposite theobject, in relation to the source, capture X-ray signal having traversedthe object. The signal captured at each point of a detector, dependingon the density and thickness of the material having by traversed by theX-ray emission.

According to the present embodiment, the X-Ray source emits a continuousspectrum of X-Rays, ranging from a lower energy range such as 10 to 70kV (+/−) up to higher energy ranges such as 60 to 250 kV (+/−).

It is to be understood that depending on particular embodiments of thepresent invention, the lower energy range may be as low as 1 kV and thehigher energy ranges may be greater that the values given above inrelation to the described embodiment.

As previously mentioned, the detectors capture the X-ray energy thattraverses the object as it is subjected to the X-rays. The detectorcomprises a first scintillator which detects a lower portion of an X-Raysignal, filter for filtering residual low range signal, and a secondscintillator which detects a higher portion of the X-Ray signal. Thehigh energy range penetrates more easily through denser materials, whilethe low energy range provides better contrast for image portionscorresponding to lighter materials.

Each of the scintillators converts the X-Ray energy to light. Eachdetector further comprises a photo-diode connected to each scintillatorin order to convert the light into an electric signal. The electricsignal is further digitized by a converter. The digitized value isassociated to a pixel of the image which represents the object.

Some error may occur in the photo-diodes' conversion of the light intoan electric signal. Indeed, a given light source may result in differentelectrical signals due to the fact that every detector card may behaveslightly differently to the presence or absence of X-Ray signal, incomparison to another detector card. This error, typically offset andgain, is corrected in order to produce a more homogenous image.

The high and low energy information is then fused, so that each pixel ofthe image results from a combination of high energy data in someproportion and low energy data in some proportion. Depending on thedensity of the material detected, it may be desirable to emphasize thelow energy information or the high energy information in suitableproportion. Indeed, as previously mentioned, the high energy rangepenetrates more easily through denser materials, while the low energyrange provides better contrast for image portions corresponding tolighter materials. The high and low energy data is thus combinedaccordingly to better illustrate particular regions of the image. Forexample, a pixel may be the result of 25% of the high energy data and75% of the low energy data because it is determined by the X-Ray signalis relatively high, meaning that it is more desirable to see contrast.The proportion of high and low energy is determined based on ranges oflow energy data value and/or high energy data value for a particularpixel.

The resulting pixel value (or signal at the pixel) is translated to acorresponding grey scale value, so as to provide a resulting image ofthe scanned object. For example, a very low pixel value may tend toappear dark grey or black, while a very high pixel value may tend toappear white or light grey. All medium pixel values are translated tocorresponding levels of grey ranging between light and dark greys.

The image may be further sharpened and/or variations therein may becorrected.

The base image is then stored in the storage 12 and ready to bedisplayed on the display screen 22. The base image may be displayed invarious formats, via the following formatting modules, shown in FIG. 1:a precious metal detection module 24, a dynamic range variation module26, a sinusoidal color map module 28, and a layer removal module 30.Each of these modules will now be described more specifically.

Precious Metal Detection and Related Features

A first display format is provided by a precious metal detection module24, on the basis of an atomic number associated to each pixel of thebase image.

An atomic number is determined based on the low energy absorption dataand high energy absorption data for a given pixel, as well as a signallevel of a source emission. The atomic numbers are thus referenced tospecific combinations of low and high energy absorption levels, for asource signal level, in a reference table. Each atomic number is furtherassociated to a specific material. The afore-mentioned high and lowenergy date associated to each pixel is thus correlated, based on thisreference table, to a type of material having been scanned at thecorresponding pixel.

Upon displaying the image, a user of the system enters a command whichspecifies one or more type(s) of metal to be observed. Each pixel beingassociated to an atomic number corresponding to each of the specifiedtype(s) is displayed within the image in a high-contrasting tone orcolor in order to highlight areas in the image corresponding to elementsmade of the specified type(s) of metals.

FIGS. 2 to 4 illustrate the operation of the precious metal detectionmodule 24 (see FIG. 1). Namely, FIG. 2 shows the contents of a suitcasewhich is scanned by an X-ray scanner. FIG. 3 shows the scanned suitcase.FIG. 4 shows the scanned suitcase when the precious metal detectionmodule 24 is activated, wherein areas 25 where precious metal isdetected is highlighted.

Thus, using different wording, there is provided in accordance with anembodiment, a method for detecting a material in an object. The methodcomprises a step of receiving, via an input port (20 or 16), a baseimage of the object comprising one or more material to be detected, thebase image being composed of pixels, each pixel comprising energyabsorption information. In another step, there is provided in a memory(for example, in database 12), one or more reference value, eachrepresenting an energy absorption of a reference material. In anotherstep, the base image is transformed, by means of a material detectionmodule (such as precision metal module 24, for example) embedded in aprocessor 14, by highlighting each of said pixels of which the energyabsorption information correlates with one of said reference materialstored in the memory (for example in database 12), based on a comparisonof the energy absorption information of each pixel with said one or morereference value stored in the memory, in order to produce adetection-enhanced image. In another step, the detection-enhanced imageis displayed on the display screen 22, showing highlighted pixelscorresponding to said one or more material to be detected.

The energy absorption information of any given pixel of the base imagecorresponds to a signal level from a source emission (for example X-Raysource emission), and may comprise an atomic number which comprises alow energy absorption component and high energy absorption component,which are in turn converted into a corresponding grey scale value forthe pixel. Accordingly, the reference value(s) stored in memory,comprises a low energy reference value and a high energy reference valuefor each reference material, and the comparison between the energyabsorption information of the pixel and the reference value(s) is madebetween the low energy absorption information and the low energyreference value; and between the high energy absorption information andthe high energy reference value, respectively.

Dynamic Range Variation and Related Features

The Dynamic range variation module 26 provides a display format wheregreyscale signals are converted to a display color, in order to betterdistinguish features in the displayed image. More particularly, variousranges of grey scale are translated to color ranges of contrastingcolor. Thus, a first range of grey scale 36 may extend from white tovery light grey, which would be converted to a spectrum 38 of reds(ranging from dark red to orange), another range of grey scale mayextend from light grey to a medium grey, which may be converted to aspectrum of yellow to green colors (ranging from orange-yellow to brightgreen), and so on an so forth, as schematically represented in FIG. 10.

It is to be understood that in accordance with alternate embodiments,the histogram stretching may be provided in various other color schemes(for example, black and white only, etc).

Moreover, the image may be further enhanced by providing a differentdynamic range on specific areas of the displayed image. Thus, uponreceiving a user selection of a region on the base image to enhance, thedynamic range variation module 26, defines a new set of color spectrumsto correspond to narrower pixel values of the selected region, as willbe better explained further below with reference to FIG. 13A to 13D.

More particularly, the dynamic range variation feature is used to betterview low signal regions of the image. These low signal regions are theresult of the presence of high attenuation materials in the scannedobject. In x-ray physics, it is well known that attenuation is acombination of thickness and density: a thin layer of dense material canyield the same attenuation as a thick layer of light material. However,thick layers of light material are uncommon in most cases.

To make the low signal regions more visible, the dynamic range of theimage is modified. This enhances the variation of the signal level inthe lower signal portion. Only the high energy data is considered, sinceit is less attenuated by dense material.

Referring to FIG. 5, there is shown a high attenuation region 32 forwhich it is desirable to gain more information about. A histogram of theimage is presented in FIG. 6. As can be seen, the image is clutteredwith undesirable information 34. All this data is set to zero, asdepicted in FIG. 7. Then, the signal levels of the remaining data isstretched so that the whole dynamic range of the image is kept, bymultiplying the signal level of the unaffected region, as represented inFIG. 8. The resulting image is shown in FIG. 9.

Referring to FIG. 10, the afore-mentioned color map further perceptuallyenhances the signal variation. The black and white colors are mapped tothe color map. The colors range from blue to red, with intermediatecolors including cyan, yellow, and orange.

The resulting image displayed is presented in FIG. 11.

On the basis of this image, a sweeping function further enhances theobserver's experience.

According to a first sweeping mode, illustrated in FIGS. 12A and 12B, aperiodic lateral sweep of the image, allows the user to analyzedifferent sections of the image with and without the enhancement. FIG.12A is a screenshot produced by the dynamic variation module at a giventime, while FIG. 12B is another screenshot produced at a later time.

According to a second sweeping mode, illustrated in FIG. 13A to 13D,there is provided a dynamic range sweep of a particular region of theimage. FIG. 13A to 13D show different screen captures taken at differenttimes of a sweep, according to this mode. An upper limit of the signallevel is gradually changed within a period of time, such that thehistogram is gradually stretched to progressively reveal the lowattenuation regions. The entire dynamic range is considered, in that theimage is completely shown at one end of the sweep (i.e. the whole rangeis displayed (0 up to a maximum value)), while nothing is shown at theopposite end (only values from 0 to 1 are displayed). As exemplified inFIG. 14, in a grey scale ranging from 0 to 1000, pixels beyond 600 arecancelled and the remaining pixels are re-scaled in a grey scale rangeextending from 0 up to 600. Similarly, as exemplified in FIG. 15, thesame may be done for a color scale, which allows variations to be moreeasily perceived by the human eye.

The Sinusoidal color map module 28 (see FIG. 1) provides a displayformat where greyscale signals are converted to a changing color scheme.Thus, regions of the image, each defined by their pixel signal value(range of grey) will be associated to its own changing color schemewhich transitions periodically in sine waves.

Advantageously, variations in the pixel signals are further enhanced.Thus, the regions of the image displayed remains static, the colors ofeach region change, so as to help better distinguish elements of theimage.

A further advantage is that some materials which would otherwise appearvery similar, for examples organic materials such as tobacco and soap,may be better distinguishable to the human eye, through this type ofdisplay by enhancing subtle variations in the texture of each of thosematerials.

FIG. 16A to 16D show different screen captures illustrating theoperation of the sinusoidal color map module 28. Each screen capture wastaken at a different time during a cycle of the sinusoidal color mapfeature by which different portions of the image are enhanced.

Thus, using different wording, there is provided in accordance with anembodiment, a method for enhancing a display of a base image of anobject. The method comprises a step of receiving, via an input port (16or 20), a base image comprising pixels. Each pixel has an intensityvalue. In another step, there is provided in a memory, referenceintensity(ies), each being associated to an output value. The base imageis transformed, by means of a conversion module embedded in a processor(for example Dynamic range variation module 26 or sinusoidal color mapmodule 28), to convert pixels of the base image into to the associatedoutput values, by correlating the intensity value of each pixel withsaid reference intensity(ies) stored in the memory, to produce aconverted image. The converted image is then displayed on a displayscreen 22.

In one alternative for colour mapping, the intensity value of thereceiving step represents an intensity level within a monochromaticscale. The reference intensity(ies) stored in the memory comprisesranges of the monochromatic scale. The output value stored comprises anoutput color for each range. The transforming step further comprisesconverting each pixel from the monochromatic scale to a correspondingone of said output color, such that the converted image is acolor-mapped image. Each range of the monochromatic scale may beassociated to a spectrum of color, the output value being selected bycorrelating a position of the intensity value of the pixel within themonochromatic range, with a corresponding position within the colorspectrum. Each range of the monochromatic scale may be associated to adistinct color. The monochromatic scale stored in the memory may furthercorrespond to contrasting colors.

In another alternative for histogram stretching, the transforming stepincludes prior to the converting step: defining a scale of intensityvalues including the intensity values of the pixels within a region ofinterest (a portion or portions of the base image, or the entire baseimage); and stretching said scale by applying a multiplying factor tothe intensity values of said pixels in the region of interest, in orderto enhance variations of in the intensity values of the pixels withinthe region of interest.

In another alternative, the transforming and displaying steps arerepeated for a plurality of iterations, in order to modify the displayedimage within a period of time (for example, for sweeping or sinusoidalcolor map features).

Layer Removal and Related Features

The layer removal module 30 (see FIG. 1) allows to strip the image of ahomogeneous layer of material in a selected region. In order to achievethis, the signal obtained at the detector level follows a Beer-Lambertlaw as depicted in FIG. 17.

An original signal only going through an object is represented by:

I ₁ =I ₀ e ^(−μ) ¹ ^(t) ¹

The signal from a threat object is represented by, i.e. the homogeneouslayer of material:

I ₂ =I ₀ e ^(−μ) ² ^(t) ²

The desired combined signal is obtained by multiplying the originalsignal with the signal from the threat itself, then dividing by thesource signal I₀:

$I_{3} = {\frac{I_{1}I_{2}}{I_{0}} = {\frac{I_{0}{^{{- \mu_{1}}t_{1}} \cdot I_{0}}^{{- \mu_{2}}t_{2}}}{I_{0}} = {\frac{I_{0}^{2}( {^{{- \mu_{1}}t_{1}} \cdot ^{{- \mu_{2}}t_{2}}} )}{I_{0}} = {I_{0}^{{{- \mu_{1}}t_{1}} - {\mu_{2}t_{2}}}}}}}$

In order to retrieve the original signal I₁ which should be present ifthe layer was not there, the following formulae applies:

$I_{1} = {{( {I_{3} \cdot I_{0}} )/I_{2}} = {\frac{I_{0}^{2}( {^{{- \mu_{1}}t_{1}} \cdot ^{{- \mu_{2}}t_{2}}} )}{I_{0}^{{- \mu_{2}}t_{2}}} = {I_{0}^{{- \mu_{1}}t_{1}}}}}$

This procedure should be implemented independently on both the high andlow energy signals.

Examples of resulting images are presented in FIG. 18.

Thus, using different wording, there is provided in accordance with anembodiment, a method for imaging an obstructed object in an image. Themethod comprises a step of receiving, via an input port (16, 20), a baseimage comprising pixels, each representing a captured signal from asource emitting a source signal I₀. Another step involves locating, bymeans of a locating module embedded in a processor 30, a region ofinterest in the base image wherein the pixels represent a combinedsignal I₃ having traversed the obstructed object and said obstructivelayer. In another step, there is provided in a memory 12, a layer signalI₂ representing a signal having traversed the obstructive layer outsideof said region of interest. A calculator (for example layer removalmodule 30) embedded in the processor 14, then isolates an originalsignal I₁ in said region of interest, by removing for each pixel in saidregion of interest, the layer signal I₂ from the combined signal I₃, onthe basis of said source signal I₀. The resulting original signal I₁represents an image of the obstructed object. The resulting image isthen displayed on the display screen 22, in which the region of interestreveals the obstructed object. The isolation is performed as explainedabove based on the Beer-Lambert Law.

It is to be understood that any of the features of the above describedcomponents, including formatting modules 24, 26, 28, 30 (FIG. 1) may becombined together or with other image processing operational features ormodules before or during the output of the image on the display screen22, as can be understood by a person skilled in the art.

Worded differently, in accordance with embodiments, there is provided animage display system for displaying a base image showing a scannedobject, the base image being composed of pixels each having a displayvalue (which may correspond to a greyscale or color value), the systemcomprising:

-   -   an input port, at a processor, for receiving the base image and        a display format selection;    -   a formatting module, integrated in the processor, for formatting        the image according to the display format selection; and    -   an output port, at the processor, for transmitting a formatted        image to be displayed.

According to a particular embodiment, each pixel of the image isassociated to an atomic number representing a composition of material.In this embodiment, the formatting module comprises a precious metaldetection module adapted to receive a selection of a metal to bedetected, to identify pixels of the image corresponding to the atomicnumber of the metal selected and to set the value of the identifiedpixels to a high-contrast color in relation to surrounding pixels, inorder to high-light regions of the image corresponding to the selectedmetal.

Alternatively or additionally, the formatting module comprises a dynamicrange variation module adapted to convert ranges of pixel values tospectrums of colors, in order to provide better contrast betweenneighboring areas in the image.

Alternatively or additionally, the formatting module comprises asinusoidal color map module adapted to define regions of the imagehaving similar pixel values and associating with each region a changingcolor scheme to be displayed in periodic variance, in order to furtherpromote distinctions between neighboring areas corresponding todifferent compositions.

Alternatively or additionally, the formatting module comprises a layerremoval module. In this embodiment, a background pixel valuerepresenting a background of the object having been scanned ispredetermined. The layer removal module is adapted to identify pixelscorresponding to the background pixel value and to set the identifiedpixels to a default value (for example, nil), so as to isolate thescanned object in the displayed image.

There may also be provided a method of displaying a base image showing ascanned object, the base image being composed of pixels each having adisplay value (which may correspond to a greyscale or color value), themethod comprising:

-   -   for receiving, at a processor via an input port, the base image        and a display format selection;    -   formatting the image according to the display format selection,        via a formatting module, integrated in the processor; and    -   transmitting, from an output port, a formatted image to be        displayed.

In the context of the present description, the term “processor” refersto an electronic circuitry that can execute computer instructions, suchas a central processing unit (CPU), a microprocessor, a controller,and/or the like. A plurality of such processors may be provided,according to embodiments of the present invention, as can be understoodby a person skilled in the art. The processor may be provided within oneor more general purpose computer, for example, and/or any other suitablecomputing device.

Still in the context of the present description, the term “storage”refers to any computer data storage device or assembly of such devicesincluding, for example: a temporary storage unit such as a random-accessmemory (RAM) or dynamic RAM; a permanent storage such as a hard disk; anoptical storage device, such as a CD or DVD (rewritable or writeonce/read only); a flash memory; and/or the like. A plurality of suchstorage devices may be provided, as can be understood by a personskilled in the art.

Embodiments of the present invention are advantageous in thatdistinctions between elements of a base image are enhanced on a displayscreen. A further advantage is that the composition of some of theelements may be more easily observed.

The above-described embodiments are considered in all respect only asillustrative and not restrictive, and the present application isintended to cover any adaptations or variations thereof, as apparent toa person skilled in the art. Of course, numerous other modificationscould be made to the above-described embodiments without departing fromthe scope of the invention, as apparent to a person skilled in the art.

1. A method for detecting a material in an object, the methodcomprising: receiving, via an input port, a base image of the objectcomprising one or more material to be detected, the base image beingcomposed of pixels, each pixel comprising energy absorption information;providing in a memory, one or more reference value, each representing anenergy absorption of a reference material; transforming the base image,by means of a material detection module embedded in a processor, byhighlighting each of said pixels of which the energy absorptioninformation correlates with one of said reference material stored in thememory, based on a comparison of the energy absorption information ofeach pixel with said one or more reference value stored in the memory,in order to produce a detection-enhanced image; and displaying, on adisplay screen, the detection-enhanced image having highlighted pixelscorresponding to said one or more material to be detected.
 2. A methodaccording to claim 1, wherein the base image is generated by capturing asource emission having traversed the object and converting said sourceemission to a pixel value.
 3. (canceled)
 4. A method according to claim2 or 3, wherein each of said one or more reference value is set for agiven signal level of the source emission and wherein said comparisonbetween the energy absorption information of the pixel and the one ormore reference value in the transforming step, takes into account saidsignal level. 5.-6. (canceled)
 7. A method according to claim 1, whereinthe energy absorption information of each pixel comprises a low energyabsorption component and a high energy absorption component.
 8. A methodaccording to claim 7, wherein the low energy absorption and the highenergy absorption components are converted into a corresponding greyscale value for the pixel.
 9. A method according to claim 7, wherein theone or more reference value comprises a low energy reference value and ahigh energy reference value for each of said reference material andwherein said comparison between the energy absorption information of thepixel and the one or more reference value in the transforming step,comprises: comparing the low energy absorption information with the lowenergy reference value; and comparing the high energy absorptioninformation with the high energy reference value. 10.-15. (canceled) 16.A non-transitory processor-readable storage medium for detecting amaterial in an object, the non-transitory processor-readable storagemedium comprising data and instructions for execution by a processor, toexecute the steps of the method, in accordance with claim
 1. 17.(canceled)
 18. A system for detecting a material in an object, thesystem comprising: an input port for receiving a base image of theobject comprising one or more material to be detected, the base imagebeing composed of pixels, each pixel comprising energy absorptioninformation; a memory for providing one or more reference value, eachrepresenting an energy absorption of a reference material; a materialdetection module embedded in a processor, the processor being incommunication with the input port and the memory, for transforming thebase image by highlighting each of said pixels of which the energyabsorption information correlates with one of said reference materialstored in the memory, based on a comparison of the energy absorptioninformation of each pixel with said one or more reference value storedin the memory, in order to produce a detection-enhanced image; and adisplay screen being in communication with the processor, for displayingthe detection-enhanced image having highlighted pixels corresponding tosaid one or more material to be detected.
 19. A method for enhancing adisplay of a base image of an object, the method comprising: receiving,via an input port, a base image comprising pixels, each pixel having anintensity value; providing in a memory, one or more reference intensity,each being associated to an output value; transforming the base image,by means of a conversion module embedded in a processor, to convertpixels of the base image into the associated output values, bycorrelating the intensity value of each pixel with said one or morereference intensity stored in the memory, to produce a converted image;and displaying the converted image, on a display screen.
 20. The methodaccording to claim 19, wherein the intensity value of the receiving steprepresents an intensity level within a monochromatic scale, wherein theone or more reference intensity stored in the memory comprises ranges ofthe monochromatic scale, wherein the output value stored comprises anoutput color for each range, and wherein the transforming comprisesconverting each pixel from said monochromatic scale to a correspondingone of said output color, such that the converted image is acolor-mapped image.
 21. The method according to claim 20, wherein eachrange of the monochromatic scale is associated to a spectrum of color,and wherein the output value is selected by correlating a position ofthe intensity value of the pixel within said range, with a correspondingposition within said spectrum of color.
 22. (canceled)
 23. The methodaccording to claim 20, wherein adjacent ranges of the monochromaticscale stored in the memory correspond to contrasting colors.
 24. Themethod according to claim 19, wherein the transforming further comprisesdefining a region of interest in the base image, and wherein the pixelsof the converting step are within the region of interest. 25.-29.(canceled)
 30. The method according to claim 19, wherein thetransforming and displaying steps are repeated for a plurality ofiterations, in order to modify the displayed image within a period oftime. 31.-32. (canceled)
 33. The method according to claim 30, furthercomprising: at a first iteration, prior to the converting step: defininga first threshold of intensity, filtering out pixels having an intensityvalue which exceeds said first threshold to keep only unfiltered pixelsof the first iteration, and multiplying the intensity values of theunfiltered pixels by a factor; and at a second iteration, prior to theconverting step: defining a second threshold of intensity different fromsaid first threshold, filtering out pixels having an intensity valuewhich exceeds said second threshold to keep only unfiltered pixels ofthe second iteration, and multiplying the intensity values of theunfiltered pixels by said factor.
 34. The method according to claim 30,wherein the output value associated to the one or more referenceintensity is further changed between successive iterations. 35.-39.(canceled)
 40. A non-transitory processor-readable storage medium forenhancing a display of a base image of an object, the non-transitoryprocessor-readable storage medium comprising data and instructions forexecution by a processor, to execute the steps of the method, inaccordance with claim
 19. 41. (canceled)
 42. A system for enhancing adisplay of a base image of an object, the system comprising: an inputport for receiving a base image comprising pixels, each pixel having anintensity value; a memory for providing one or more reference intensity,each being associated to an output value; a conversion module embeddedin a processor, the processor being in communication with the input portand the memory for transforming the base image in order to convertpixels of the base image into the associated output values, bycorrelating the intensity value of each pixel with said one or morereference intensity stored in the memory, and to produce a convertedimage; and a display screen displaying the converted image.
 43. A methodfor imaging an obstructed object in an image, the method comprising:receiving, via an input port, a base image comprising pixels, eachrepresenting a captured signal from a source emitting a source signalI₀; locating, by means of a locating module embedded in a processor, aregion of interest in the base image wherein the pixels represent acombined signal I₃ having traversed the obstructed object and saidobstructive layer; providing, in a memory, a layer signal I₂representing a signal having traversed the obstructive layer outside ofsaid region of interest; isolating, by means of a calculator embedded inthe processor, an original signal I₁ in said region of interest, byremoving for each pixel in said region of interest, the layer signal I₂from the combined signal I₃, on the basis of said source signal I₀, theresulting original signal I₁ representing an image of the obstructedobject; and displaying on a display screen, a resulting image from saidoriginal signals I₁, wherein the region of interest reveals theobstructed object.
 44. The method according to claim 43, wherein theisolating step is based on the Beer-Lambert Law.
 45. The methodaccording to claim 44, wherein the original signal I₁ is obtainedaccording to the following equation:$I_{1} = {{( {I_{3} \cdot I_{0}} )/I_{2}} = {\frac{I_{0}^{2}( {^{{- \mu_{1}}t_{1}} \cdot ^{{- \mu_{2}}t_{2}}} )}{I_{0}^{{- \mu_{2}}t_{2}}} = {I_{0}^{{- \mu_{1}}t_{1}}}}}$wherein I₁=I₀e^(−μ) ¹ ^(t) ¹ , where μ₁ represents an attenuationcoefficient of the obstructed object and t₁ represents a thickness ofthe obstructed object; and wherein I₂=I₀e^(−μ) ² ^(t) ² , where μ₂represents an attenuation coefficient of the obstructive layer and t₂represents a thickness of the obstructive layer. 46.-48. (canceled) 49.A non-transitory processor-readable storage medium for imaging anobstructed object in an image, the non-transitory processor-readablestorage medium comprising data and instructions for execution by aprocessor, to execute the steps of the method, in accordance with claim43.
 50. (canceled)
 51. A system for imaging an obstructed object in animage, the system comprising: an input port for receiving a base imagecomprising pixels, each representing a captured signal from a sourceemitting a source signal I₀; a locating module embedded in a processor,the processor being in communication with the input port for locating aregion of interest in the base image wherein the pixels represent acombined signal I₃ having traversed the obstructed object and saidobstructive layer; a memory for providing a layer signal I₂ representinga signal having traversed the obstructive layer outside of said regionof interest; a calculator embedded in the processor, for isolating anoriginal signal I₁ in said region of interest, by removing for eachpixel in said region of interest, the layer signal I₂ from the combinedsignal I₃, on the basis of said source signal I₀, the resulting originalsignal I₁ representing an image of the obstructed object; and a displayscreen for displaying a resulting image from said original signals I₁,wherein the region of interest reveals the obstructed object.